1. Field of the Invention
The present invention relates to cutting tools such as a milling cutter, an end mill and a lathe tool, and more particularly to those tools in which indexable cutting inserts are releasably secured to a tool body using an insert-holding member such as a support member, a seat member and a wedge member.
2. Prior Art
In the inserted cutters which are widely used for processing a metal workpiece, indexable cutter inserts formed of a hard material such as cemented carbide are releasably attached to the recesses formed in the tool body. For securing the cutter inserts to the recesses, various clamping methods are hitherto known. Typical methods involve causing a clamp screw to pass through the insert to be threaded into a recess; or pressing the insert against the recess by means of a wedge member or a clamp block. Furthermore, in recent years, in order to avoid the damage of the tool body caused by the fracturing of the insert, the insert is received in a support member of a hard material such as cemented carbide, and is secured to the tool body by being received in the support member. Moreover, even in the case where the insert is directly attached to the tool body using a clamp screw, a seating member formed of a hard material is often interposed between the insert and the recess of the tool body to prevent the recess from being damaged when the insert is fractured.
Thus, the support member and the seat member must have great hardness in order to ensure positive protection of the tool body and to enhance the wear resistance of the members themselves, and hence cemented carbide is hitherto used as a material for forming these members. However, inasmuch as the compression molding of cemented carbide involves many operational steps, the manufacturing cost is unduly increased. In addition, since the cemented carbide has high brittleness, the members formed of this material are susceptible to fracturing due to impacts encountered during the cutting operation. Moreover, setting aside the seating member which is formed into a simple plate, it has been difficult to prepare a support member of a desired shape. More specifically, the support member must usually be relatively intricate in shape, e.g., an aperture which is inclined with respect to the surface must be formed. However, since the cost for the compression molding of such an intricate support member is unduly high, the support member practically manufactured has been limited in shape.
Furthermore, a wedge member, which is used for pressing the insert against the recess, has been hitherto formed by precision casting using a material less hard than the cemented carbide, and hence no difficulty arises in forming wedge members of an intricate shape. However, since the precision of the casting is not high enough, various after-working operations such as sanding are required after the casting operation, so that the manufacturing cost is unduly high.